Hi, I am new to this software and want to understand more, why in the layers column there is a layer called “Background” when I load Krita? I know what layers are and how to add them etc and use them, but when looking at YouTube tuition videos, I can see no evidence of a “Background” layer being in the layers column. Does it serve a different purpose that an ordinary layer; do I need it and; can I delete it and just work on the layers I have added?
Hello and welcome to the forum 
You have two very similar questions in two topics, this one and the other:
The default (as installed) option for creating a new image is to create it with a ‘background’ paint layer that is covered in white paint with a single empty/transparent paint layer over it. This is ‘background as raster layer’.
This is a good ‘starter situation’ for many people who want to paint an image in the same was that you might paint on paper (but with layers above the paper, not painting on the paper itself).
If you remove the background layer then you’ll see the checkerboard pattern which represents transparency in the final composited image.
The background layer is locked at first to prevent people painting on it or deleting it. Any attempt to do either of those things often results in confusion or concern for beginners who aren’t familiar with the concepts of transparency and the checkerboard convention for indicating transparency.
You can delete it if you want to (after you unlock it). You can do whatever you like to it. It’s your computer, your krita installation and your artwork.
Some people, for whatever reason, don’t like to see the checkerboard and prefer to see a white sheet instead and so there is also the option of ‘background as canvas colour’ and here, if there is no paint on any of the layers, you see a white sheet, the base canvas colour.
If you want to produce .png images with transparency in them then the ‘background as canvas colour’ is of no use and you need to use ‘canvas as raster layer’ and then turn off the visibility of the background layer.
‘Background as fill layer’ is the other option where a background layer (i.e bottom of the layer stack) is made not as a Paint Layer but as a Fill Layer.
A fill layer is a special type of layer that can have not only have a colour fill on it but also a pattern and other things.
If you do right-click → Properties on a fill layer, you’ll be able to do all sorts of things to it.
Also, a fill layer has a built-in transparency mask and if you paint on it then you’ll be painting on that transparency mask. Try it to observe the effect.
A fill layer is quite specialist and also very powerful and useful, if you need or want that sort of thing.
If you’re familiar with multi-layer digital image painting/manipulation applications then you’ll soon understand the different options and behaviours.
Whoever made that video may have removed the standard background layer, for whatever reason, or they may have renamed it.
They, and you, are free to do what is wanted according to what is needed and what is preferred.